Re: Old for scope rules (/forScope-) don't work with STL declarations?

"Heinz Ozwirk" <>
Sun, 3 Dec 2006 10:55:02 +0100
"Nimai" <> schrieb im Newsbeitrag

In trying to get hundreds of legacy C++ projects compiling under VS
2005 from 2003, I turned off the proper for-loop scoping rules using

It works fine with for loops declaring ints, but I got an undeclared
identifier error when referencing a for-declared STL iterator. I tried
std::string too, out of curiosity, and it doesn't behave properly
Here's a meaningless example meant to demonstrate the problem only:

for( int xx=0; xx<10; ++xx)
result = (xx==10); // WORKS FINE
for( std::string yy; !yy.empty(); yy.clear())
yy.clear(); //IN VS2005: error C2065: 'yy' : undeclared identifier'

Any idea what might be going on here? Why would STL classes be any
different than built-in types? (I tried declaring my own struct in the
for loop, and it worked as int did.)

Don't use the forLoop switch in VS 2005. Rewrite your code to become valid
C++ code. This takes some time, but it is not really difficult. Just find
all definitions of variables in the initalization part of the for statement
and move them out of the for statement.

You should be happy that VS2005 enforces the scope of UDTs in for loops even
if you explicitly ask for the old behaviour. The old (non-standard)
behaviour of definitions in for statements never worked with UDTs. The dtor
of such variables had been called at the end of the for statement, but you
could still access them outside their scope. So, in the example above,
calling yy.clear() has always been undefined behaviour. You have been lucky,
that your program actually seemed to work.


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